1. Field of the Invention
The subject invention relates generally to drilling and/or servicing subterranean wells for recovery of hydrocarbon-bearing fluids and more specifically to a method and apparatus for drilling and/or servicing subterranean wells with rotating coiled tubing.
2. Description of the Related Art
Historically, subterranean wells have been drilled by rotating a bit attached to the end of jointed pipe or tubing sections. The jointed pipe string is rotated from the surface, which rotation is transferred to the bit. As the rotating bit drills into the earth, additional sections or joints of pipe must be added to drill deeper. A significant amount of time and energy is consumed in adding and removing new sections of pipe to the drill string.
Coiled tubing, such as described in U.S. Pat. No. 4,863,091, is available in virtually unlimited lengths and has been used for a variety of purposes in the exploration and production of hydrocarbons from subterranean wells. Coiled tubing has not, to date, supplanted jointed pipe for drilling operations.
It is believed that the most common use of coiled tubing in drilling operations involves the use of a motor or other energy source located at the end of tubing adjacent the drill bit. One type of motor is a mud motor that converts pressurized drilling mud flowing through the coiled tubing into rotational energy for the drill bit. In this type of system, the coiled tubing itself does not rotate. For example, U.S. Pat. No. 5,360,075 is entitled “Steering Drill Bit While Drilling A Bore Hole” and discloses, among other things, a motor powered drill bit at the end of coiled tubing that can be steered by torsioning the tubing. The article Introduction to Coiled Tubing Drilling by Leading Edge Advantage International Ltd. is believed to provide an overview of the state of the art of drilling using non-rotating coiled tubing, a copy of which may be found at www.lealtd.com. The substance of that article is incorporated by reference herein for all purposes.
Another approach for drilling with coiled tubing is taught in U.S. Pat. No. 4,515,220, which is entitled “Apparatus and Method for Rotating Coil Tubing in a Well” and discloses, among other things, cutting the coiled tubing away from the spool before the tubing can be rotated for drilling operations.
U.S. Pat. No. 6,315,052 is entitled “Method and a Device for Use in Coiled Tubing Operations” and appears to disclose an apparatus that physically rotates a spool of coiled tubing about an axis to thereby drill the well bore. U.S. Pat. No. 5,660,235 is similarly entitled “Method and a Device for Use in Coil Pipe Operations” and discloses, among other things, maintaining the coiled tubing in substantial alignment with the injector head as the tubing is spooled and unspooled by rotating the reel about a pivot point and/or translating the reel relative to the injector head.
The present invention builds on the prior art and is directed to an improved method and apparatus for drilling and/or servicing subterranean wells with rotating coiled tubing.